This invention relates to the treatment of oleaginous seed or fatty animal material, and more particularly to the treatment of defatted oleaginous seed or animal material to form a desolventized proteinaceous product which may be recovered and used industrially.
Oleaginous seed materials, such as soybeans, cottonseed, peanuts, sesame seeds, sunflower seeds, rape seeds, and the like, contain proteinaceous material of a highly nutritious nature and have found many uses in the plastics, paper and food industry. Soybeans, for example, after oil extraction, have been desolventized to recover the proteinaceous matter for various and diverse industrial processes.
Traditionally, the extraction of fats and oils has been and continues to be effected by means of washing the fat and oil-containing substances with a suitable liquid extraction solvent until the desired concentration of the resulting solution is obtained. This solution is then treated in evaporators and condensers which respectively separate the extraction solvent in vapor form from the solution and convert the vapor back to liquid form for re-use in the extraction process. The defatted residual solids left after the oil or fat is extracted are generally impregnated with extraction solvent, thereby rendering them unusable as a source of nutritious protein, until desolventizing is accomplished.
A complete proteinaceous or carbohydrate extraction process necessarily includes an extraction step, a spent flake desolventizing step, and a miscella evaporation step. The final use to which the solvent impregnated residual solids are to be put will determine the nature and type of desolventizing step which is employed,. In particular, the defatted flakes may be contacted with an acidic solution to dissolve the nonproteinaceous matter, including certain enzyme systems, ash, flavoring ingredients and carbohydrates with the residual substance being utilized as a proteinaceous composition in the food industry. Such a system is described in U.S. Pat. No. 2,881,076 to Sair. Alternatively or in conjunction with the above, the defatted flakes may be treated with an aqueous alcohol solution to extract the nonproteinaceous matter (primarily carbohydrates). However, such processes suffer from large liquid-to-solid ratios which place excessive loads on the desolventizer apparatus. Moreover, the steam requirements to recover the solvent have proven to be excessive. The requirements for additional heat transfer capabilities in the process result in massive expenditures of heat. The spent flake desolventizing step may also be comprised of the application of superheated steam in a partial vacuum to evaporate the extraction solvent from the spent flakes and carry it out of the desolventizer in conjunction with the steam.
Traditionally, the miscella of fat or oil in the extraction solvent is separated by use of heat and a vacuum provided by a steam ejector to produce oil and solvent-laden waste ejector steam. The solvent-laden waste ejector steam is then treated in condensers which convert the vapor back to a liquid form for use in the extraction process. The solvent then must be reheated in order to be re-used in the extraction process. This results in substantial heat loss, as well as requiring additional heat transfer capabilities within the processes.